In the movement region of a loop resectoscope adjacent the high frequency cutting loop, it is known to provide the end of the resectoscope sleeve with a sleeve portion formed from an electrical insulating material to avoid the possibility of electrical short circuits caused by contact between the sleeve and the loop, which is energized with a high frequency voltage, and which can come in contact with the sleeve. Such insulating pieces are customarily produced from a glass fiber-reinforced plastic which has rigidity of form and which is break-resistant to a reasonable degree.
The poor temperature resistance of this insulating material is, however, a disadvantage. Considerable thermal damage to the plastic can result, especially at the region of the distal edge of 2the insulating piece with which the still-energized loop very frequently comes into contact at very high temperatures, necessitating frequent replacement of the insulating portion or the entire shaft.
One structure of the general type with which the invention is concerned is shown in German OS No. 25 02 863 and U.S. Pat. No. 4,060,086 in which an effort has been made to avoid the kind of damage discussed above by providing a ceramic insert sleeve encased in an outer plastic sleeve of the insulating portion. The highly heat-resistant ceramic material is intended to be sufficiently temperature resistant and, by thermal insulation, is intended to protect the surrounding plastic against overheating and, in turn, the plastic is intended to ensure break resistance.
This structure has the disadvantage, however, of being extraordinarily expensive. In addition, it should be noted that the thermal insulating characteristics of ceramic are not sufficient under all circumstances to prevent the plastic material surrounding it from temperature damage. Thus, detachment of the ceramic insert and resulting destruction of the insulating piece can occur. In addition, the protection of the solid-body ceramic sleeve against splintering is not sufficient. In the event of inexpert handling of the device, and especially in the event of compression of the insulating piece, the ceramic insert can be shattered.